Cooling jacket assemblies for control rod drive mechanisms of nuclear reactors are used to cool the stator of a control rod drive motor tube. The cooling jacket assembly usually surrounds the stator of the control rod drive mechanism and consists of a metal sleeve or inner casing having a helical peripheral water channel or groove formed in its outer surface by metal cutting and grinding operations. The water channels or grooves are closed by an outer sleeve or jacket by pressing or brazing the sleeve to the inner casing. Cooling water is fed into and through the formed channels and is discharged therefrom through suitable fittings. The forementioned outer sleeve seals the formed water channel and when water is circulated therethrough the inner casing is cooled which in turn cools the stator of the control rod drive mechanism. Clearly, this known cooling assembly involves the machining on the outer diameter of the inner casing to form a spiral circumferential rectangular groove. This machining operation is time-consuming and expensive. Furthermore, the snug-fitting of the outer sleeve over the grooved inner casing does not always provide a tight seal between adjacent machined grooves. This causes short circuiting of the cooling water and cuts down on the efficiency of the cooling operation.
Another type of cooling jacket assembly is manufactured by machining a helical groove in the outside diameter of the inner casing which groove accepts with a good snug fit a continuous copper tube. The copper tube is positioned in the machined groove and is then brazed into position. Water is flowed through the copper tube cooling the inner casing which in turn cools the stator of the control rod drive mechanism. This method again involves the expensive and time-consuming process of forming a helical groove in the inner casing material added with the further operation of brazing copper tubing into the grooves.